The present invention relates to an inspecting apparatus for inspecting the printing face condition of letters, graphics, and the like, printed on the surface of the object to be inspected, such as a compact disk (hereinafter referred to as CD), or the like.
Generally, in order to display recording contents on the CD, maker name, music name, player name, and so on, are printed on the surface of the CD. As an inspecting apparatus for inspecting as to whether or not the printing condition is defective, Japanese Unexamined Patent Publication No. 94517/1993 discloses "Image Inputting Apparatus for Optical Inspecting Apparatus", wherein the defects of the printing face are detected with the use of a plurality of moving picture apparatuses (two CCD cameras). Also, in the description of the publication, four CCD cameras are used to take pictures with one CD being divided into four portions for higher resolution and speed. In the publication, whether the camera is for color use or for black and white use is not described. The construction wherein four color CCD cameras are used is not realistic in terms of cost, or the like. So, it is considered that the construction is composed of four black and white cameras.
Conventionally, there is a method of taking pictures with the use of one color camera as a moving picture apparatus in the printing face inspecting apparatus, or with the use of four back and white cameras, as described in the conventional example, with one CD being divided into four portions. However, the method has the following problems.
In the former wherein one color camera is employed, the resolution is so low that the micro defects cannot be detected. Increase of the number of the color cameras (to four, for example) for improving the resolution would make image pickup apparatus expensive. In the color camera, the price of the image processing apparatus positioned in the rear stage of the image pickup apparatus becomes higher as compared with the black and white camera. The image processing apparatus becomes higher in price in accordance with the number of the cameras. The advantage of the color camera is three times in information amount (the color information of R, G, B) as compared with the black and white camera, thus making it possible to effect a color judging operation.
In the latter, the price per camera and per image processing apparatus is lower as compared with that of the color camera. The higher resolution for image pickup operation using four black and white cameras can detect micro defects. Although the black and white camera can tell the density of the color, the color cannot be judged because color information is lacking.
As described above, both the former and the latter have advantages and disadvantages, respectively. The present invention is provided to settle the defects of the conventional image pickup apparatus. The present invention realizes a printing face inspecting apparatus having a low-priced image pickup apparatus, wherein the micro defects on the printing face can be detected with the black and white camera, and the color judgment can be effected with the color camera